The present invention relates to a catalyst for use in the removal of sulphur, nitrogen, contaminating metals, asphaltenes and Conradson carbon from heavy crudes and residues and, more particularly, a method for the preparation of the catalyst and a process for the treatment of heavy crudes and residues with the catalyst.
The use of catalysts for the hydrotreatment of hydrocarbons of petroleum origin has been known for some time. Known processes are suitable for the reduction of the high metal content, the high asphaltene and Conradson carbon content, the high viscosity and the high sulphur and nitrogen contents of heavy crudes and residues. In addition, these processes are important since they facilitate an increase in yield of liquid fractions which are of greater commercial value.
High metallic contents in crudes and residues are very harmful in other petroleum refining processes, such as hydrocracking, hydrodesulphurization and catalytic cracking, since it poisons the catalysts, while the asphaltenes cause blocking of the catalyst bed thereby reducing its useful life, thus increasing the costs of operation.
The catalysts used in the hydrotreatment of heavy crudes and residues generally contain a metal from Group VIII of the Periodic Table of the elements, particularly cobalt or nickel, together with a metal from Group VIB of the Periodic Table, particularly molybdenum or tungsten. These metals are normally used in the form of oxides or sulphides and are supported on a carrier of a refractory oxide, generally gamma alumina.
Various methods have been reported for the preparation of catalysts and various processes disclosed for the improved hydrotreatment of heavy crudes and residues with catalysts.
U.S. Pat. No. 3,232,887 to Pessimis et al. discloses an aqueous solution of metals of Group VIB, stabilized with orthophosphoric acid for depositing on/or impregnating silica or alumina carriers. The presence of phosphorus in the catalyst obtained from this process increases the denitrogenation and desulphurization of the petroleum hydrocarbons. However, the patent fails to disclose a catalyst for nor does it give examples of application to heavy crudes and residues or of hydrodemetallization.
U.S. Pat. No. 3,649,523 to Bertolacini et al. discloses a catalytic composition formed by hydrogenation of a member of Group VIB and a metal selected from Group VIII of the Periodic Table of elements, supported on alumina with large pores. This catalyst is used for a hydrocracking process of heavy fractions. However, there is no disclosure drawn to the hydrotreatment of heavy crudes and residues having high metal contents.
U.S. Pat. Nos. 3,749,663, 3,755,150 and 3,755,196 to Mickelson disclose a catalytic formulation for the conversion of hydrocarbons and for desulphurization comprising a refractory oxide carrier impregnated with metals from Group VIB, Group VIII and phosphorus. The ratio by weight of P/MoO.sub.3 is disclosed as between 0.1 and 0.5, so as to obtain an increase in hydrodesulphurization activity in hydrocarbons containing at least 100 ppm of sulphur. Mickelson does not disclose the P/Mo surface ratio for his catalyst. The weight ratio disclosed is not solely responsible for the catalyst activity observed.
U.S. Pat. No. 3,686,137 to Gatti discloses a catalyst for hydrogenation, desulphurization and denitrogenation of hydrocarbons. The catalyst is prepared by means of an aqueous solution of metals from Groups VIB and VIII stabilized with phosphoric acid. No examples are given in the patent for hydrodemetallization with such a catalyst.
U.S. Pat. No. 4,003,828 to Eberly Jr. discloses a process for removing metals and sulphur from heavy crudes and residues by using a catalyst which contains a hydrogenation component and an alumina carrier containing 1 to 16% by weight of phosphorus oxide as P.sub.2 O.sub.5. The carrier is prepared by mixing a cogel of phosphorus oxide and alumina. This patent does not disclose a catalyst where the phosphorus oxide is incorporated in the carrier in the same stage as metal impregnation.
U.S. Pat. No. 4,317,746 to Richardson discloses a hydrotreatment catalyst formed from nickel, molybdenum and phosphorus as active components supported on alumina partially hydrated with water vapor. The catalyst is used for the desulphurization and denitrogenation of hydrocarbons. This catalyst is not disclosed as applicable to the hydrotreatment of heavy crudes and residues.
Accordingly, it is the principle object of the present invention to provide an improved catalyst for use in the hydrotreatment of heavy crudes and residues.
It is a particular object of the present invention to provide an improved catalyst for use in the hydrotreatment of heavy crudes and residues characterized by improved catalytic activities such as hydrodesulphurization, hydrodenitrogenation, hydrodemetallization and the conversion of asphaltenes and Conradson carbon.
It is a further object of the present invention to provide a method for the preparation of a catalyst used in the hydrotreatment of heavy crudes and residues.
It is a still further object of the present invention to provide a process for the treatment of heavy crudes and residues with a catalyst.
Further objects and advantages will appear hereinbelow.